Brainstem: Medulla oblongata

1. Overview of the brainstem – subdivisions 2. Embryonic development of the brain stem3. Medulla oblongata – external features4. Internal structure of the medulla oblongata

Prof. Dr. Nikolai Lazarov 2

� 3 subdivisions:� medulla oblongata� pons� midbrain

� 10 cranial nerves attached(with the exception of nn. I and II)� motor and sensory

innervation: face&neck� pathway for:

� all fiber tracts passing up and down

� 3 laminae: tectum, tegmentum, basis� neurological functions:

� survival� breathing� digestion� heart rate� blood pressure

� arousal� being awake and alert

General organization Brain stem

Prof. Dr. Nikolai Lazarov 3

Embryologic development� Embryonic origin:

�mesencephalon � midbrain� rhombencephalon:

�metencephalon �

pons&cerebellum�myelencephalon �

medulla oblongata

Brain stem

Prof. Dr. Nikolai Lazarov 4

Medulla oblongata – external features� synonyms: bulbus, myelencephalon� shape – pyramidal or conical

� size:� 3 cm longitudinally� 2 cm transversally� 1.25 cm anteroposteriorly

� 2 parts:� lower, closed part� upper, open part

� functions:� relay station of motor tracts� contains respiratory,

vasomotor and cardiac centers� controls reflex activities such as

coughing, gagging, swallowing and vomiting

Medulla oblongata

Prof. Dr. Nikolai Lazarov 5

Medulla oblongata – anterior aspect� anterior median fissure� pyramid � pyramidal decussation� olive� anterolateral sulcus � hypoglossal nerve (XII)� retroolivar sulcus � nn. IX, X and XI

Medulla oblongata

Prof. Dr. Nikolai Lazarov 6

Medulla oblongata – posterior aspect� posterior median sulcus� caudal, closed part – obex:

� gracile fascicle � gracile tubercle� cuneate fascicle � cuneate tubercle� posterior intermediate sulcus� posterolateral sulcus� tuberculum cinereum

Medulla oblongata

Prof. Dr. Nikolai Lazarov 7

Medulla oblongata – posterior aspect� cranial, open part – rhomboid fossa:

� medullary striae of fourth ventricle � obex

� sulcus limitans� hypoglossus triangle� vagus triangle� area postrema� vestibular area, acoustic tubercle � pons� inferior cerebellar peduncle � cerebellum

Medulla oblongata

Prof. Dr. Nikolai Lazarov 8

Medulla oblongata – internal structure� white and grey matter� olive:

� inferior olivary nuclear complex� posterior column nuclei:

� nucleus gracilis� nucleus cuneatus� internal arcuate fibers � sensory

decussation � medial lemniscus� bulbothalamic tract

� external arcuate fibers� posterior � cuneocerebellar tract� anterior � bulbocerebellar tract

Medulla oblongata

� reticular nuclei:� raphe nuclei, pallidus, obscurus & magnus – SERergic (B1-B3)

Prof. Dr. Nikolai Lazarov 9

Grey matter: nuclei of the cranial nerves� glossopharyngeal nerve (IX):

� inferior salivatory nucleus� nucleus ambiguus (IX, X, XI)� solitary tract nucleus (VII, IX, X)

� vagus nerve (X): � dorsal motor nucleus of the vagus

� accessorius nerve (XI)� hypoglossal nerve (XII):

� hypoglossal nucleus

� trigeminal nerve (V):� spinal trigeminal nucleus

Medulla oblongata

Prof. Dr. Nikolai Lazarov 10

White matter: ascending and descending tracts

� descending (corticobulbar) tracts:� corticospinal tract � pyramidal decussation� reticulospinal tract

� ascending tracts:� cuneocerebellar tract� anterior and posterior spinocerebellar tracts� anterior and lateral spinothalamic tracts� spinotectal tract

� mixed tracts:� dorsal longitudinal fasciculus:

� descending hypothalamic axons� ascending visceral sensory axons

Medulla oblongata

Prof. Dr. Nikolai Lazarov 11

Thank you…